SWAN 350 > resurrecting a dead radio and almost there but need guidance

Discussion in '"Boat Anchor" & Classic Equipment' started by N3SWR, Oct 8, 2021.

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  1. N3SWR

    N3SWR Ham Member QRZ Page

    Thanks to anyone willing to offer me some help here. Short story is I was "tasked" to help a fellow ham check out this radio before it was simply plugged in and avoid letting the magic smoke out of the supply. I'm not new to tubes and definitely not electronics so I said sure no problem.

    This is a Swann 350 with the standard 117x external supply. Having never even seen one of their radios made this intriguing. I went through the usual good visual inspection and discovered very swelled electrolytics with broken off leads in the supply. So I placed an order and recapped the entire supply. All voltages on the rail indicated normal values with minimal ripple. From here I went and gave this a careful air blast to remiove the dust as there was a decent film everywhere. Next I cleaned all the switch and pot contacts with DeOxide (well actually it's Cramolin - I still have a bottle of that). This is all what I consider normal maintenance for older equipment. Unfortunately the radio seems to have been stored in some dusty damp basement before it landed on my lap so i have my work cut out for me it seems...

    Next came the dim bulb test with everything hooked up to the house mains via a variac and slowly brought it to life. All seemed to indicate a good living setup.

    A quick test on receive only with my doublet antenna and she came to life after a good minute warmup. Actually it was a good sounding radio! The radio was dead in any transmit/tune mode from what I could tell. Back to the supply and i discover the 12Vdc is gone at the Jones plug. Took that apart and discovered a broken wire. that's all fixed now. Back to testing the radio and a quick click of the mic and I could tell the radio was dead for transmit. A swing of the receive/tune cw switch confirmed that as the radio definitely dimmed, solenoids clunked and my outside security cameras and internal settings went haywire. Yup - she transmitted alright but only in tune/cw mode. I jumped the PPT switch to be sure and no results there. I'll admit I'm not 100% positive on the actual working condition of the mic here and i don't have a spare to play with. A quick look with a DMM and I do get some resistance readings and the PPT button does work it seems. I'll assume for the moment the mic is good. I popped the top of the solenoid and it's very clean in there but I did spray those contacts to be good. I pulled out the old Hickok 539 and did test all but the power tubes and I didn't find and concerns at the moment.

    So I'm looking for some pointers from those that might have seen this problem or simply know of where to look. I troubleshot myself into a corner as they say. Time to take a step back and re-evaluate things as I've learned over the years.

    So now that you know the story - sorry it turned out to be a bit long - I just wanted to cover all corners here so we don't go down the rabbit hole of 101 questions of did you do this or that. Just being helpful to those interested. Thanks in advance!
  2. KA0HCP

    KA0HCP XML Subscriber QRZ Page

    Sounds like you have done a great job thus far!

    While not directly addressing the question at hand, my next step would be to check resistor values in place and see whether they have drifted out of spec, roughly 20%. b.
  3. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Kind of a rough test.:p Use a wattmeter and dummy load to see what kind of RF output it generates in TUNE. With normal drive and optimal tuning, should be around 150W.
    Be sure the mike plug is wired correctly. The 1/4" phone plug "tip" is PTT (closure to ground), the "ring" is the mike audio and obviously the sleeve is ground for both. There's no "electronics" in that circuit at all, the PTT line from the mike jack connects directly to one end of each relay coil K1 & K2 with the other ends of those coils directly connected to +12Vdc. To check operation of K2, you can just use an Ohmmeter to assure the screw terminals "C" and "T" close (short together) when you activate the PTT. If they don't, the relay isn't activating or the contacts are bad.
    The only tubes in the lineup that are used only on XMIT and not on receive are V2, V13 and V15, other than the PA driver and final amplifier tubes V3, 4 and 5. If you had good RF output in TUNE, then V2, 3, 4 and 5 should be okay as they're used in TUNE/CW as well as in SSB. V13 and the mike amp tube V15 are used only on SSB.

    There's a test point voltage chart on page 14 of the manual that provides all the test points required to debug the SW-350. Alignment instructions are page 11-13 and they work.
    KA9P likes this.
  4. N3SWR

    N3SWR Ham Member QRZ Page

    LOL thanks for the pointers. Yea it was definitely a rough test. The wife was NOT happy as the RF field that thing generated actually messed up some internal software settings in my camera DVR console.
    All is back to normal now. I'll get back to radio hopefully this weekend. I actually want to experience this radio working as I've heard some good things about it from those that own them.
  5. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    It's a simple but pretty solid rig.

    If you like Hallicrafters stuff, the SR-150 is around the same vintage and also quite nice and similar in operation. The Swan runs a bit more TX power (assuming good, new tubes).
  6. N3SWR

    N3SWR Ham Member QRZ Page

    Thanks for this as that was a problem now fixed. Solenoids now latch up properly.

    Unfortunately still no output from the rig and I did check with two power meter setups just for sanities sake. The entire receive section appears good and works fine. Since I always chop a problem in half to discover which way to go in search of something, I'm not going to fiddle with the receive sections for the moment. I'm at work so the radio is not in front of me at the moment but I do have the operation/maintenance manual here. Going from the transmitter tuning section, I recall I managed to make it to part 6, achieved 50mA current for PA BIAS and such. It's hereafter that things seemed to not follow the intended results so well and I wonder if going down the road of a full alignment would be proper form to catch this bug. I do need to check the power tubes as I've never taking them out of the chassis even. I suspect something is open or dirty in the path. While going through the tuning process I sure can seem to load up the amp, dim the lights and dip the grid but - there is definitely no RF output. I'll know more in the next few days hopefully.

    Thanks for the help thus far!
  7. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    I'd check all the test point voltages listed at the tube socket pins first, before alignment.

    Something as simple as a small open RF choke can kill the transmitter and might be a $1 repair that doesn't require alignment.
    KW4H likes this.
  8. KW4H

    KW4H Platinum Subscriber Platinum Subscriber QRZ Page

    ^^THIS. Granted, I've never worked on a Swan 350; however, from having repaired many electronic devices over the years such as TVs, VCRs, Stereos (had a business doing that in the 80s and 90s) as well as various ham-related gear, I can say from personal experience that the causes of failures are usually relatively simple -- as long as a piece of gear hasn't been experimented on by a mad scientist. If that Swan looks clean and unmolested, you've probably got a single, rather simple failure somewhere. It may not be easy to find, but it will be easy to fix. And if you get totally stumped, here's a trick that's worked for me countless times: circle back around to the basics even if you've been there before. Can't count the number of times I've revisited a power supply only to find something I missed.

    73 - Steve
    Last edited: Oct 12, 2021
  9. KN7FM

    KN7FM Ham Member QRZ Page

    Good luck finding a good 6360 tube. Dual plates and unbalancing by deflection of electron beam.
    Wow haven't played with a Swan 350 for nearly 40 yrs. Best of luck to you!
  10. KA5IPF

    KA5IPF Ham Member QRZ Page

    Ah, and remembering a quote from the past. "Anyone know where the Swan net is? Reply, just sit tight they will drift by sooner or later"

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